Acrylonitrile polymer composition and stabilized with zinc oxalate, zinc acetate, or chromium acetate



United States Patent O fiice 3,988,932 Patented May 7, 1963 ACRYLONITRILE POLYMER COMPOSITION AND STABILIZED WITH ZINC OXALATE, ZTNC ACE- TATE, OR CHROMTUM ACETATE Terry W. Tarkington, Decatur, and Carlton D. Whitt,

Athens, Ala., assignors, by mesne assignments, to Monsanto Chemical Company, a corporation of Delaware No Drawing. Filed Dec. 2, 1960, Ser. No. 73,268 6 Claims. (Cl. 260-4575) This invention relates to the stabilization of acrylonitrile polymers and compositions thereof. More particularly, it relates to the stabilization of acrylonitrile polymers and compositions thereof which have a tendency to develop color when exposed to either natural sunlight or various types of artificial light.

Fibers, filaments and other shaped articles produced from acrylonitrile polymers have :a tendency to develop a considerable color change when exposed to either natural sunlight or various types of artificial light. This color change in the case of fibers occurs when the fibers are in either the bleached or the unbleached state and gives an unstable background color for the fiber either in dyed or undyed textile end uses.

The mechanism which causes color changes has not been definitely ascertained, although it is thought to be fairly well established. Sunlight, and to a lesser extent artificial light, contains not only visible light but also infra-red and ultra-violet radiations. The absorption of light causes changes mainly manifest in a deterioration of fiber properties, such as tensile strength and color fastness. This absorption and resultant photo-chemical degradation usually proceeds very slowly for most undyed articles, possibly due to less absorption of ultra-violet radiations. However, the color of articles made from bleached undyed fiber must be stable to light and not show a change in color which is primarily an undesirable darkening effect. The presence of certain types of dyes markedly increases the rate of degradation and reduces the working life of the fiber. The dye seems to be able to pass the absorbed light energy on to effect a quicker destruction of the fiber molecules. Dyed materials are faded by absorbed visible and ultra-violet radiation up to a critical wave length and above this point, radiation is non-actinic even if it is strongly absorbed. Some dyes also have a synergistic effect on other dyes even though the individual dyes may be acceptable when used alone. Textile auxiliary materials may also have a synergistic effect on some dyes. The net result of this is that the dyer is not only confused about which dyes and auxilitary agents to use but also has a much more limited range of dyes and textile auxiliary agents that he can work with. Even though some dyes can be found which do not accelerate this photo-degradation, the background color change in the fiber due to the photo-degradation, even with these dyes, is enough to cause undesirable color changes in the dyed article. Whatever may be the reason for color changes, it results in compositions and products of undesirable standards and therefore, any light stabilizing agents which would reduce this color change upon light exposure would be highly desirable.

Accordingly, it is an object of the present invention to minimize undesirable color formation in acrylonitrile polymers and compositions thereof. Another object is to minimize undesirable color changes in acrylic fibers. It is also an object of the invention to provide solutions of acrylonitrile polymers and articles produced therefrom having improved color characteristics by the addition of certain chromium and zinc compounds to the acrylonitrile polymer solution or to the fiber finish bath. Other objects and advantages will be apparent from a consideration of the description of the invention which follows hereinafter.

In general, the objects of the invention are accomplished by adding as a light stabilizing agent, a small amount of chromium acetate, zinc acetate, zinc oxide or zinc oxalate to an acrylonitrile polymer solution or to the finish bath. This stabilizing agent present in the polymer is likewise present in the shaped articles produced therefrom and minimizes or prevents the development of objectionable color occurring on exposure of the shaped articles to natural sunlight or artificial light.

The total amount of stabilizing agent which may be employed may range from about 0.025- to 2.0 percent based on the total weight of the polymer. However, it is preferred to employ from about 0.1 to 1.0 percent by weight to give the best light stabilizing action. The stabilizing agent may be added to the spinning solution or to the finish bath by any suitable means.

The compositions of the instant invention may be prepared in a varying temperature range. Thus the compositions may be prepared by mixing the polymer, a suitable solvent, and the stabilizing agent at any suitable temperature and thereafter heating the mixture up to the boiling point of the solvent to insure complete dissolution of the polymer.

Any polyacrylonitrile solvent may be used in practicing the instant invention. Among the solvents preferably suitable are N,N-dirnethylformarnide, N,N-dimethylacetamide, ethylene carbonate, dimethyl sulfoxide, nitromethane, gamma-butyrolactone, aqueous zinc chloride, aqueous solutions of sodium thiocyanate, sulfuric acid, aqueous solutions of nitric acid, and the like. These solvents generally function as solvents for acrylonitrile polymers at temperatures of from about 25 C. to the boiling point of the polymer solvent mixtures.

The use of these stabilizing agents, in accordance with the present invention, effects improvement in color characteristics in all solutions of acrylonitrile polymers and articles produced therefrom. The invention is applicable not only to polyacrylonitrile, but also to copolymers, in terpolymers and blends thereof, particularly those containing at least percent by weight of polymerized or copolymerized acrylonitrile. Such polymeric materials include acrylonitrile fiber-forming polymers with readily dyeable basic copolymers, the blend having an overall polymerized acrylonitrile content of at least 80 percent by weight.

For example the polymer may be a copolymer of from 80 to 98 percent of acrylonitrile and from 2 to 2.0 percent of another copolymerizable mono-olefinic monomer. Suitable copolymerizable mono-olefinic monomers include acrylic, alphachloroacrylic and methacrylic acids, the acrylates, such as methylmethacrylate, ethylmethacrylate, butylmethacrylate, methoxymethyl methacrylate, beta-chloroethyl methacrylate, and the corresponding esters of acrylic and alpha-chloroacrylic acids; vinyl chloride, vinyl fluoride, vinyl bromide, vinylidene chloride, 1- chloro 1 bromoethylene; methacrylonitrile; acrylamide and methacrylamide; alpha-chloroacrylamide, or monoalkyl substitution products thereof; methyl vinyl ketone; vinyl carboxylates, such as vinyl acetate, vinyl chloroacetate, vinyl propionate, and vinyl steer-ate; N-vinylimides, such as N-ivinylphthalimide and N-vinylsuccinirnide; methylene malonic esters; itaconic acid and itaconic ester; N-vinyl carbazole; vinyl furan; alkyl vinyl esters; vinyl sulfonic acid; ethylene alpha, beta-dicarboxylic acids or their anhydrides or derivatives, such as diethylcitraconate, diethylrnesaconate; styrene; vinyl naphthalene; vinyl-substituted tertiary heterocyolic amines such as the vinylpyridines and alkyl-substituted vinylpyridines for example, Z-Vinylpyridine, 4-vinylpyridine, 2-methyl-5-vinylpyridine, and the like; l-vinylimidazole and alkyl-substituted l-vinylimidazoles, such as 2-, 4-, or S-methyl-lvinylimidazole, vinylpyrrolidone, vinylpiperidone, and other mono-olefinic copolymerizable monomeric materials.

The polymer can be a ternary interpolymer, for example, products obtained [by the interpolymerization of acrylonitrile and two or more of any of the monomers, other than acrylonitrile, enumerated above. More specifically, and preferably, the ternary polymers contain from 80 to 98 pencent of acrylonitrile, from 1 to percent of a vinylpyridine or a l-vinylirnidazole, and from 1 to 18 percent of another copolymerizable mono-olefinic substance, such as methacrylonitrile, vinyl acetate, methylmethacrylate, vinyl chloride, vinylidene chloride, and the like.

The polymer can also be a blend of polyacrylonitrile or a copolymer of from 80 to 99 percent acrylonitrile and from 1 to 20 percent of at least one other mono-olefinic copoly-merizable monomeric substance with from two to fifty percent of the weight of the blend of a copolymer of from 30 to 90 percent of a vinyl substituted tertiary heterocyclic amine and from 10 to 70 percent of at least one other mono-olefinic copolymerizable monomer. Preferably, when the polymeric material comprises a blend, it will be a blend of from 80 to 99 percent of a copolymer of 80 to 98 percent acrylonitrile and from 2 to 20 percent of another mono-olefinic monomer, such as vinyl acetate, which is not receptive to dyestufi, with from 1 to 20 percent of a copolymer of from 30 to 90 percent of a vinyl-substituted tertiary heterocyclic amine, such as a vinylpyridine, a l-vinylimidazole, or a vinyl lactam, and from 10 to 70 percent of acrylonitrile to give a dyea'ble blend having an overall vinyl-substituted tertiary heterocyelic amine content of from 2 to 10 percent, based on the weight of the blend.

While the preferred polymers employed in the instant invention are those containing at least 80 percent acrylonitrile, generally recognized as the fiber-forming acrylonitrile polymers, it will be understood that the invention is likewise applicable to polymers containing less than 80 percent of acrylonitrile. Polymers containing less than 80 percent acrylonitrile are useful in forming fibers, lacquers, coating compositions and molded articles, in all of which applications light stabilization is important.

The polymers, useful in the practice of the present invention, may be prepared by any conventional polymerization procedures, such as mass polymerization methods, solution polymerization methods, or aqueous emulsion procedures. The articles manufactured from the solutions formed therewith may be produced by well-known conventional methods, for example, the wet-spinning method for producing fibers. If it is desired to produce shaped articles from the acrylonitrile polymer solutions of the present invention which have a modified appearance or modified properties, various agents may be added to the solutions to accomplish these effects prior to the fabrication of the articles without any ill effects thereon. Such added agents might be pigments, dyes, anti-static agents, fire-retarding agents, etc.

In order to simulate exposure to natural sunlight, the acrylic fiber samples in the examples of this invention were exposed for 20 Standard Fade-O-Meter hours in an Atlas Fade-O-Meter by the methods recommended by the Technical Manual of the American Association of Textile Chemists and Colorists, in the annual issue for 1957 published by the Howes Publishing Co., 44 E. 23rd St., New York City.

The tests for color indicative of bleached light stability used throughout the examples which follow consist of 4 nology Press, Massachusetts Institute of Technology, in 1936.

The instant invention is further illustrated by the following specific examples, in which all proportions and percentages are by weight unless otherwise specified.

EXAMPLE I Twenty kilograms of a copolymer of 94 percent acrylonitrile and 6 percent vinyl acetate were added to 60 kilograms of N,N-dimethylacetarnide and 140 grams of titanium dioxide. The mixture was stirred and heated to C. and maintained at that temperature until a solution was formed. The resultant solution was then spun into a fiber by the wet spinning method with zinc acetate added to the finish bath at a rate equivalent to 0.1 weight percent zinc acetate, based on the fiber weight. At the same time a control sample fiber was produced from the same cop'olymer and solvent in the same amounts without the addition of zinc acetate. The values for purity and brightness of the control fiber and the stabilized fiber are set forth in Table I below.

Table I Percent Stabilizer Based on Fiber Weight Bleached Light Stability Brightness Purity Control 14. 4 11.1 0.1 Zinc acetate 5. 7 5. 5

EXAMPLE II Table II Bleached Light Stability Percent Stabilller Based on Fiber Weight A Brightness A Purity Control l1. 9 10. 6 0.2 Zinc acetate. 2.1 4. 1 0.2 Zinc oxide 2. 1 3. 2 0.2 Zinc oxalate 1.9 3. 3 0.2 Chromium acetate 2. 8 3. 8

As many apparently widely ditierent embodiments of this invention may be made wtihout departing from the spirit and scope thereof, it is to be understood that the same is not to be limited to the specific embodiments thereof except as defined in the appended claims.

We claim:

1. A new composition of matter comprising a polymer containing in polymerized form at least 80 percent of acrylonitrile and up to 20 percent of at least one copolymerized mono-olefinic monomer and, as a light stabilizing agent from 0.025 to 2.0 percent, based on the weight of the polymer, of a compound taken from the group consisting of zinc acetate, zinc oxalate and chrornium acetate.

2. A new composition of matter comprising a copolymer having at least 80 percent of aorylonitrile and up to 20 percent of vinyl acetate, dissolved in a solvent therefore, and, as a light stabilizing agent from 0.1 to 1.0 percent of zinc acetate based on the total weight of the polymer solution.

3. A new composition of matter comprising a polymer blend of 80 to 99 percent of (A) a copolymer containing 80 to 98 percent of acrylonitrile and 2 to 20 percent of vinyl acetate and 1 to 20 percent of (B) a copolymer containing 10 to 70 percent of racrylonitrile and 30 to 90 percent of 24methyl-5-viny1pyridine, said blend being so proportioned that the 2-methyl-5-vinylpyridine comprises irom 2 to 10 percent by weight of blend dissolved in a solvent therefore, and as a light stabilizer, from 0.025 to 2.0 percent zinc oxalate based on the weight of the polymer.

4. An acrylonitrile polymer fiber containing, as a light stabilizing agent, from 0.1 to 1.0 percent, based on the weight of the polymer, of zinc oxalate.

5. An aerylonitrile polymer fiber containing, as a light stabilizing agent, from 0.1 to 1.0 percent, based on the weight of the polymer, of zinc acetate.

6. An acrylonitrile polymer fiber containing, as a light stabilizing agent, from 0.1 to 1.0 percent, based on the Weight of the polymer of chromium acetate.

References Cited in the file of this patent UNITED STATES PATENTS 2,385,890 Spanagel Oct. 2, 1945 2,517,694 Merion Aug. 8, 1950 2,687,393 Trementozzi Aug. 24, 1954 2,688,008 Chaney Aug. 31, 1954 2,688,012 Chaney Aug. 31, 1954 2,710,846 Dietrich et a1. June 14, 1955 2,715,763 Marley Aug. 23, 1955 2,739,139 Gabler Mar. 20, 1956 2,949,437 'Hobson Aug. 16, 1960 2,970,884 Stanton Feb. 7, 1961 2,971,937 Ham Feb. 14, 1961 2,975,022 Euler Mar. 14, 1961 OTHER REFERENCES Cosmetics Science and Technology, by Sagarin, Interscience Publishers Inc., New York, 1957. 

1. A NEW COMPOSITION OF MATTER COMPRISING A POLYMER CONTAINING IN POLYMERIZED FORM AT LEAST 80 PERCENT OF ACRYLONITRILE AND UP TO 20 PERCENT OF AT LEAST ONE COPOLYMERIZED MONO-OLEFINIC MONOMER AND, AS A LIGHT STABILIZING AGENT FROM 0.025 TO 2.0 PERCENT, BASED ON THE WEIGHT OF THE POLYMER, OF A COMPOUND TAKEN FROM THE GROUP CONSISTING OF ZINC ACETATE, ZINC OXALATE AND CHROMIUM ACETATE. 